Canadian Forest Service Publications
Histopathological examination of western hemlock dwarf mistletoe infected with potential biocontrol fungi. 1999. Deeks, S.J.; Shamoun, S.F.; Punja, K. Canadian Journal of Plant Pathology 21: 200.
Issued by: Pacific Forestry Centre
Catalog ID: 5252
Available from the Journal's Web site. †
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Western hemlock dwarf mistletoe (Arceuthobium tsugense subsp. tsugense) causes reduction in vigor, growth, and wood quality. Potential biological control fungi are being investigated to reduce mistletoe development. Two fungi that parasitize A. tsugense (Nectria neomacrospora and Colletotrichum gloeosporioides) were evaluated using an in vitro screening method. Seeds of dwarf mistletoe were germinated on tissue culture medium (Harvey's medium), while the other half of the plate contained water agar on which fungal growth was initiated from a mycelial plug. Mistletoe tissues were fixed in phosphate buffer with glutaraldehyde 1, 2, 3, 7, and 14 days postcontact with two fungi and prepared for light microscopy. Fungal colonization was mainly restricted to the endosperm and outer cell layers of the radicle, with heavy colonization of the radicle tip. Cushion development, cell wall degradation, and inter-and intra-cellular colonization were evident for both fungi. Experiments are underway to challenge dwarf mistletoe callus with these fungi.